Footage later released by the ministry showed some of the former hostages dressed in white gowns and red headscarves as they were greeted by officials in the high security Green Zone in Iraq's capital, Baghdad.

They were then seen in the video boarding a Qatar Airways plane at Baghdad airport. State media later confirmed that they had landed in Doha.

What's known about the kidnapping?

The group was seized in December 2015 while on a licensed hunting trip near the border with Saudi Arabia.

The hostages were abducted when gunmen swept into their camp at dawn in four-by-four vehicles.

The hunting party is widely believed to include one or several more prominent members of the Qatari royal family, although they have not been identified.

Image copyrightGetty ImagesImage caption
The Asian houbara bustard, found in Iraq, is highly prized in the Arab Gulf states

They were hunting the Asian houbara bustard, akin to a small turkey, using falcons trained to home in on their quarry.

Why are they being released?

Their release is said to be connected to a complex deal in Syria involving the evacuation of four besieged towns, which was announced earlier this week.

However, the interior ministry has not provided details confirming this.

The Guardian newspaper has reported that an Iraqi militia with strong ties to Iran, a key backer of the Syrian government and its ally Hezbollah, was holding the Qatari hunters.

It says the deal involves the Syrian Islamist group Ahrar al-Sham, Iran, the Lebanese militant group Hezbollah and Qatar.

Also on Friday, a spokesman for Ahrar al-Sham told Reuters that the Syrian government was going to release 500 prisoners into rebel-held territory, as part of a swap deal.

What is the 'four towns' deal?

It is an agreement to end the sieges of four towns - two surrounded by pro-government forces, two by rebel and Islamist fighters - in eastern Syria.

Foah and Kefraya are mainly Shia Muslim, government-held towns, close to the border with Lebanon, which have been besieged since March 2015.

Madaya and Zabadani are rebel-held towns in the north-east, which have been besieged since June 2015 by the Syrian army and fighters from Lebanon's Shia Muslim Hezbollah movement.

Conditions have been desperate, especially in Madaya and Zabadani, with severe shortages of food, medicine and fuel. International aid deliveries have been infrequent and required careful negotiation. Government air drops have eased the situation in Foah and Kefraya somewhat.

Thousands of evacuees from Foah and Kefraya have also been held up at a staging point for 48 hours, but a rebel involved in the operation told AFP that the buses had left after the news of the release of government-held prisoners.

According to AFP, the current phase of evacuations involves 8,000 people from Foah and Kafraya, and 2,500 civilians and rebels from Madaya and Zabadani.